1. Field of the Invention
The present invention relates to a structure in the earth for protecting one or more deep-based missiles from damage during an attack and for allowing the post-attack egress and launching of the missile, and to a method of forming an egress passageway for the missile through the structure.
2. Description of the Prior Art
Previous proposals have been made that intercontinental ballistic missiles be based so deep in rock that they would be invulnerable to attack by even very large and very accurate thermonuclear warheads. For example, they might be based in underground chambers excavated in dense rock at a depth of 1200-1500 meters below the earth's surface at a location where 600-900 meters of rock nearest the earth's surface is soft, porous, and shock-absorbant. The surface burst of a 60 Megatonne warhead on such a deep-based missile complex might be expected to produce a zone of ruptured and sheared rock having a radius of 900 meters and a depth of 600 meters from the point of explosion. This would collapse any pre-existing exits that would otherwise permit egress and launching of a deep-based missile. Therefore, it has been proposed that rock-boring machinery be provided to those manning such a deep underground missile base, and that after such an attack they would use this machinery to bore their way out to the surface of the earth through the overlying rock. Thereby they would in due time create a passageway through which their missiles could be brought to the surface for launching. The unsuitability of such a basing system for launching a surprise attack, and its invulnerability to surprise attack might be expected to reduce the probability that a surprise attack would be launched at all.
But in order to be a deterrent, such missiles should pose a credible ultimate threat to a would-be attacker. The well-known difficulties of boring through rock and particularly through highly broken rock would be expected to reduce the credibility of such a nuclear deterrent and would substantially increase the cost of such a basing system.